General purpose household cleaning compositions for hard surfaces such as metal, glass, ceramic, plastic and linoleum surfaces, are commonly available in both powdered and liquid form. Powdered cleaning compositions consist primarily of builder or buffering salts such as phosphates, carbonates, silicates, etc, and are particularly useful for solid and organic soil removal. Liquid cleaning compositions consist primarily of water and/or solvents, and are particularly useful for grease and oily soil removal.
Linear alkylbenzene sulfonate (LAS) is widely used as surfactant in hard surface cleaning compositions. A potential disadvantage of LAS, however, is that under hard water conditions, i.e., calcium levels greater than about 150 parts per million, it can interact with cationic water hardness ions, such as calcium, thereby becoming inactivated through precipitation. While this is a problem common to anionic surfactants, LAS is especially sensitive to water hardness ions.
Although not wishing to be bound by any theory, the literature indicates that the aforementioned interaction can best be understood by considering the micellar structure of anionic surfactants, e.g., LAS. Repulsive forces between negative charges in the sulfonate group lead to a higher critical micelle concentration (CMC) than, for example, with a nonionic surfactant. CMC is the surfactant concentration at which micellar formation begins. Stated otherwise, the negative charge of LAS retards micellar formation and shifts the equilibrium towards the monomer. A relatively high monomer concentration in solution results thereby; this is significant because precipitation between calcium ion and LAS occurs only with the monomer.
It has been found that in both liquid and powdered hard surface cleaning compositions, secondary alkyl sulfate can be used as an anionic surfactant component in place of LAS with the advantages being increased tolerance for water hardness ions, good soil removal properties, higher active raw material, i.e., less water, and better color of anionic raw material.